Rock drill

ABSTRACT

A rock drill and more particularly an independent rotation rock drill assembly having an improved method and apparatus for initiating reciprocable movement of the piston thereof.

United States Patent [191 Bailey Jan. 15, 1974 1 ROCK DRILL [76]Inventor: Edward A. Bailey, RFD N0. 2, Box

37, Newport, NH. 03773 [22] Filed: Nov. 23, 1970 [21] Appl. No.: 92,028

[52] US. Cl. 91/6, 91/232 [51] Int. Cl. F0lb 25/00, F011 21/02 [58]Field of Search 91/6, 224, 232, 239;

[56] References Cited UNITED STATES PATENTS 3,279,326 10/1966 Harvey eta1. 91/224 2,999,482 9/1961 7 3,038,449 6/1962 Murphy, Jr. et a1. 91/63,596,560 8/1971 Butterworth 91/6 1,940,143 12/1933 Overly 91/2323,118,348 l/1964 Kline 91/232 1,662,576 3/1928 .leschke 91/239 FOREIGNPATENTS OR APPLICATIONS 972,080 10/1964 England 91/6 941,041 3/1956Germany 91/6 Primary Examiner-Martin P. Schwadron Assistant Examiner-A.M. Zupcic V AttorneyE. Wallace Breisch [57] ABSTRACT A rock drill andmore particularly an independent r0- tation rock drill assembly havingan improved method and apparatus for initiating reciprocable movement ofthe piston thereof.

5 Claims, 2 Drawing Figures ROCK DRILL Some rock drills presently in useare classified as independent rotation" rock drills which have aseparate air motor carried thereby for imparting rotation to a strikingbar through suitable gearing. Independent rotation rock drills providefor reciprocable movement of the piston head therewithin in a variety ofmanners, for example, the more or less conventional kicker port valvetypes or the valveless cycle type employing a plurality of passagewaysfor channeling air under pressure to respective piston impart andretract passageways. An example of the latter mentioned valveless cycleindependent rock drills is found and illustrated in U.S. Pat.Application Ser. No. 59,290, filed July 29, 1970, and assigned to thesame assignee as is this invention now U.S. Pat. No. 3,666,024.

With such rock drills as described hereinabove problems often arise inthe initial starting phase thereof for under circumstances known tothose skilled in the art the piston head has a tendency at times tofreeze when pressurized air is initially supplied thereto. The

freeze of the piston head can best be viewed as a condition wherein thepressures in the impact and retract chambers are virtually equal or thepressure differential therebetween is too small to initiate the cyclicmovement of the piston. The tendency of the piston to freeze occurs mostfrequently when the rock drill is in a substantially horizontalposition, however, freezing of the piston can occur in any position ofthe rock drill.

By means of the present invention which includes a connection from afluid pressure line, other than the main fluid pressure line forsupplying air under pressure for the reciprocable movement of the pistonhead, directly to either the impact or retraction passageways, thehereinabove mentioned problem of piston freeze is substantiallyovercome.

These and other objects and advantages of the present invention willbecome more readily apparent from a reading of the following descriptionand drawings in which:

FIG. 1 is a portion of a central longitudinal vertical section through arock drill embodying the principles of the present invention and showingthe piston in an intermediate cyclic position thereof; and

FIG. 2 is a plan view of a portion of a rock drill viewed on lines 2-2of FIG. 1.

An elongated and pneumatically powered rock drill embodying theprinciples of this invention and of a type shown and described in U.S.Pat. Application Ser. No. 59,290, filed July 29, 1970, and assigned tothe same assignee as is this invention now U.S. Pat. No. 3,666,024comprises an elongated annular motor cylinder 12 which axially receivesa stepped cylindrical piston l4 therewithin for delivering impact loadsto a suitable striking bar 16 which is suitably adapted to carry a drillsteel (not shown). The motor cylinder 12 is disposed intermediate a rearback or casing head 18 and a front or forward yoke 20. Cylinder l2,piston 14, casing head 18 and yoke 20 are generally coaxial with respectto a longitudinal axis X-X of rock drill 10.

A plurality of circumferentially spaced exhaust portals 22 extendradially through cylinder 12 intermediate the axial ends thereof. Anelongated annular motor cylinder lining 24, having an outer diameterthereof substantially equal to the inner diameter of cylinder 12, isaxially received within the interior of cylinder 12 and oriented suchthat the axial ends thereof are in approximate transverse alignment withrespective axial ends of cylinder 12. Liner 24 additionally has aplurality of circumferentially spaced exhaust portals 26 which extendradially therethrough intermediate the axial ends thereof and when liner24 is received and aligned within cylinder 12, portals 26 are in opencommunication with respective portals 22 of cylinder 12. The abovedescribed alignment of liner 24 within cylinder 12 is retained in anysuitable manner, for example, a plurality of radially inwardly extendingset screws 28 which engagingly communicate between liner 24 and cylinder12.

Liner 24 is of stepped cylindrical longitudinal cross section which hasa constant outer diameter and includes a rear portion 30 and anincreased inner diameter forward portion 32. An annular interiorshoulder 34 is formed where portions 30 and 32 meet intermediate theaxial ends of liner 24. A stepped cylindrical buffer ring 36 whichincludesa rearward portion 38 having an outer diameter thereofsubstantially equal to the inner diameter of liner portion 32 iscoaxially received within portion 32 such that the rearwardmost endthereof engages shoulder 34 and the forwardmost end thereof istransversely aligned with a forwardmost end of portion 32. A forwardportion 40 of buffer ring 36 has an outer diameter thereof less than theouter diameter of portion 38 and extends axially and forwardly from theforwardmost end thereof.

An exterior shoulder 42 is formed at the intersection of portions 38 and40. The annular forward yoke 20 includes a flange 44 at the rearward endthereof which has an inner diameter thereof substantially equal to theouter diameter of buffer ring portion 36 and as such, flange 44, engagesshoulder 42 and the forward ends of cylinder 12 and liner 24 therebyretaining buffer ring 36, cylinder 12 and liner 24 in the abovedescribed relative positions.

A disc shaped rearward supporting ring 46 having an outer diameterthereof shown as equal to the outer diameter of motor cylinder 12 iscoaxially disposed intermediate the rearward end of cylinder 12 and theforward end of casing head 18. With support ring 46 positioned asdescribed above, the travel of piston head 14 is limited to thatdistance between the forwardmost end of ring 46 and the rearwardmost endof buffer ring 36.

Piston 14 comprises a rear portion 50 having an outer diameter thereofsubstantially equal to the inner diameter of the rear portion 30 ofliner 2-4 and an elongated reduced diameter stem 52 which extendscoaxially forwardly from piston portion 50. Piston 14 is slidablyreceived within liner 24 and upon such reception the stem 52 thereof isslidably received within a coaxial through bore 54 which extendslongitudinally through buffer ring 36. Stem 52 has a plurality ofcircumferentially aligned and spaced, outwardly open grooves 56 spacedabout the outer periphery and intermediate the axial ends thereof. Asshown grooves 56 have a generally rectangular cross section with thelong sides thereof extending generally parallel to the longitudinal axisX-X of rock drill 10.

A pneumatic fluid pressure source (not shown) provides a supply ofpneumatic pressure fluid, such as air, to rock drill 10. To retract thepiston 14 from the down stroke or impact position thereof, that is theposition wherein head 14 is in engagement with the rear end of strikingbar 16, pressurized air flows: from the source; through a conduit 57;through a passageway 58 in casing head 18 communicating between therearward and forward ends thereof; through a plurality of bores 60 whichare circumferentially spaced about ring 46 and inwardly spaced from theouter periphery thereof and open into an outwardly open groove 62 in aforward end portion of ring 46; through groove 62; and through aplurality of passageways 64 which communicate between groove 62 andrespective ones of a plurality of liner passageways 66. Linerpassageways 66 are shown as radially outwardly open circumferentiallyspaced grooves which extend axially along the outer periphery of liner24 generally parallel to axis XX. The forward ends of passageways 66terminate intermediate the axial ends of the forward portion 32 of liner24. The pressurized air flows through passageway 66 and into respectivepassageways 68. Passageways 68 extend radially inwardly from the forwardends of respective passageway 66 and open into a passageway 70 in bufferring 36 communicating between the inner and outer periphery thereof. Thepressurized air flows; through passageway 66; through passageways 68;through passageway 70 and into the grooves 56 about the outer peripheryof stem 52.

Spaced axially forwardly from passageway 70, a passageway 72 in bufferring 36 also communicates between the inner and outer periphery thereof.When piston head 14 is in the down stroke or impact position discussedhereinabove, passageways 70 and 72 register with grooves 56 adjacent therearward and forward ends thereof respectively. The pressurized air frompassageway 70 flows: through grooves 56; through passageway 72; andthrough a plurality of radially extending passageways 74 in liner 24communicating between the inner periphery thereof and the forward end ofrespective ones of a plurality of liner passageways 76. Linerpassageways 76 are shown as radially outwardly open circumferentiallyspaced grooves which extend axially along the outer periphery of liner24 generally parallel to axis X--X. The rearward ends of passageways 76terminate axially intermediate the forward axial end of rear portion 30of linear 24 and exhaust portals 26.

A plurality of radially inwardly extending passageways 78 in liner 24communicate between respective liner passageways 76 adjacent therearward ends thereof, and the inner periphery of liner 24. With piston14 in the downstroke or impact position passageway 78 opens into aretracting chamber 80 which is defined by and comprises that areabetween the inside diameter of liner 24 and the outside diameter of stem52 axially intermediate rear piston portion 50 and the rearward end ofbuffer ring 36. Pressurized air flows from linear passageway 76; throughpassageways 78 and into retracting chamber 80 whereat such pressurizedair reacts against the forward annular surface of piston head portion50, and accordingly, urges the piston l4 axially rearwardly to theupstroke position thereof.

During the initial portion of the upstroke travel of piston head 14 animpact chamber 82, which is defined by and comprises that area of theinner periphery of liner 24 axially intermediate the rearward end ofpiston 14 and the forward end of supporting ring 46, is in opencommunication with the aligned exhaust portals 22 and 26 and as such thepressure within area 82 during such initial upstroke travel issubstantially atmospheric. The term substantially atmospheric is usedherein for portals 22 and 26 exhaust into an encompassing mufflerassembly 84 and a slight back pressure somewhat higher than atmosphericwill exist within muffler assembly 84. Assembly 84 is opened toatmosphere at portals 86 spaced about the periphery thereof. The airwithin impact chamber 82 will exhaust through portals 22 and 26 for theportion of the upstroke travel of piston 14 which maintains opencommunication between portals 22 and 26 and chamber 82.

FIG. 1 illustrates the operation of the impact motor when piston 14 isin a position intermediate the upstroke and downstroke position thereof.In the intermediate piston head position, stem grooves 56 are no longerin communication with passageway 72 and, as such, the flow ofpressurized air therethrough and eventually into retracting chamber isdiscontinued. The open communication between impact chamber 82 andportals 22 and 26 is also discontinued by the outer periphery of pistonportion 50 registering radially adjacent to portals 26. Chamber 80 andthe passageways leading thereto comprise a substantially isolated systemand accordingly the pressurized air within chamber 80 begins to expandand as such continues to apply pressure to the forward annular surfaceof piston head portion 50 thereby maintaining the rearward or upstrokemovement thereof. Upon such continued upstroke the air within chamber82, which chamber 82 also comprises a substantially isolated system,compresses and offers a resistance to the upstroke movement ofthe pis'ton head 14. The expansion of the air within chamber 80 coupled with theupstroke momentum imparted to piston head 14 when passageway 72 wasstill in communication with the fluid pressure source, will provide anupstroke force to piston 14 greater than the resistance presented by thecompression of air within chamber 82, thereby forcing piston 14 to theupstroke position thereof. The resistance offered by the compression ofair within chamber 82 provides an instantaneous rebound force to aid inthe downstroke travel of piston 14 as hereinafter described.

In the upstroke or retracted position of piston head 14 passageway 70 isin open communication with grooves 56 adjacent the forward ends thereof.A passageway 88 in buffer ring 36 which is spaced axially rearwardly ofpassageway 70 communicates between the inner and outer periphery of ring36. When piston 14 is in the upstroke position passageway 88 is in opencommunication with grooves 56 adjacent the rearward ends thereof.

To move the piston 14 from the retracted or upstroke position thereofinto impact engagement with the striking bar 16, pressurized air flows:through passageway 70; and grooves 56; through passageway 88; andthrough a plurality of passageways 90 in liner 24 which communicatebetween passageway 88 and respective ones of a plurality of linerpassageways 92 adjacent the forward ends of passageways 92. Linearpassageways 92 as shown comprise radially outwardly opencircumferentially spaced grooves which extend axially along the outerperiphery of liner 24 generally parallel to axis urges X.

A plurality of radially extending passageways 94 in liner 24 communicatebetween respective liner passageways 92, adjacent the rearward endsthereof and axially intermediate the forward end of supporting ring 46and exhaust portals 26, and the inner periphery of liner 24. With pistonhead 14 in the upstroke position passageways 94 are in opencommunication with the impact chamber 82. Pressurized air flows throughpassageways 92; and through passageway 94 into impact chamber 82 whereatsuch pressurized air reacts against the rearward surface of pistonportion 50 and, accordingly, urges piston 14 forwardly into impact withstriking bar 16.

During the initial portion of the downstroke travel of piston 14 theretract chamber 80 is in open communication with aligned exhaust portals22 and 26 and as such the pressure within chamber 80 during such initialdownstroke travel is substantially atmospheric. The air withinretracting chamber 80 will exhaust through portals 22 and 26 for theportion of the downstroke travel of piston 14 which maintains opencommunication between portals 22 and 26 and chamber 80.

When piston 14 is in an intermediate position during the downstrokecycle thereof, grooves 56 are no longer in communication with passageway90 and, as such, the flow of pressurized air therethrough and eventuallyinto impact chamber 82 is discontinued. The open communication betweenretracting chamber 80 and portals 22 and 26 is also discontinued by theouter periphery of piston head portion 50 registering radially adjacentportals 26. The pressurized air within chamber 82 begins to expand, and,as such, continues to apply pressure to the forward annular surface ofpiston head portion 50 thereby maintaining the forward or downstrokemovement thereof. Upon such continued downstroke movement the air withinchamber 80 compresses and offers a resistance to the downstroke movementof the piston 14. The expansion of the air within chamber 82 coupledwith the downstroke momentum imparted to piston 14 when passageway 90was still in communication with the fluid pressure source will provide adownstroke force to piston 14 greater than the resistance presented bythe compression of air within chamber 80, thereby forcing piston 14 intothe full downstroke position thereof, that is, into impact with strikingbar 16. The resistance offered by the compression of air within chamber80 eventually decreases the force with which piston 14 strikes strikingbar 16, however, the pressure within chamber 80 offers an instantaneousrebound force to aid in the upstroke travel of piston 14 as hereinbeforedescribed.

Striking bar 16 is rotated by a pneumatically operable independent motor100. The output from motor 100 is delivered to striking bar 16 in anysuitable manner, for example, as shown and illustrated in the abovementioned U.S. application Ser. No. 59,290 now U.S. Pat. No. 3,666,024.Motor 100 is suitably supported in any suitable manner and as shown inFIG. 2 is positioned within a forward radially outwardly expandedportion of muffler assembly 84. Air under pressure flows from a source(not shown) and through a rotation motor conduit 101 which communicatesbetween the source and motor 100. Conduit 101 is independent from impactconduit 57 and pressurized air is selectively and respectively suppliedto each of such con-,

piston 14 greater than the resistance present by the compression of airwithin chamber 82, thereby forcing piston 14 to the upstroke positionthereof. Likewise, when piston 14 is in the intermediate position of thedownstroke travel thereof, the expansion of air within chamber 82coupled with the downstroke momentum imparted to piston 14 whenpassageway was still in communication with the fluid pressure sourcewill provide a downstroke force to piston 14 greater than the resistancepresented by the compression of air within chamber 80, thereby forcingpiston 14 into the full downstroke position thereof, that is, intoimpact with striking bar 16. It was additionally noted that theresistance offered by the compression of air within respective chambersoffers an instantaneous rebound force to aid in the cyclic travel of thepiston 14. While the hereinabove setforth cyclic operation of piston 14is generally true, experience has found that the piston 14 has atendency at times to freeze when pressurized air is initially suppliedthereto. The freeze of the piston can best be viewed as a conditionwherein the pressure within the impact chamber 82 is virtually equal tothe pressure within the retract chamber 80 or the pressure differentialbetween such chambers is too small to initiate cyclic movement of thepiston 14. The tendency of the piston 14 to freeze occurs mostfrequently when the rock drill 10 is in a substantially horizontalposition, however, freezing of the piston can occur in any position ofthe rock drill 10. The freezing will generally occur when the piston 14is in a position intermediate the upstroke and downstroke positionthereof. In such an intermediate position stem grooves 56 are not incommunication with either passageway 72 or 88 and hence the flow ofpressurized air into either the impact or retraction chambers isdiscontinued and also the open communication between the portals 22 and26 and a respective one of the chambers 80 and 82 is discontinued by theouter periphery at piston head portion 50 registering radially adjacentportals 26. As previously mentioned the passing of the piston 14 throughthe intermediate cyclic position would have no effect on the cyclicmovement thereof because of the momentum imparted thereto when arespective chamber was in communication with the pressurized sourcecoupled with the expansion of the pressurized air within such a chamber;however, when initially starting the impact motor the momentum impartedto the traveling piston is somewhat less because the rebound force whichaids the travel of the piston 14 is not initially present in the system.Thus, the piston 14 travels to the intermediate position and freezes.Other factors affecting the start up of the cyclic movement of thepiston 14 include cold and non-circulating lubricant, impurities withinthe lubrication system, and the like.

By means of the start-up bolster assembly 104 of the present inventionthe hereinabove mentioned problem of piston head freeze during start upoperations is substantially eliminated. As shown start-up bolsterassembly 104 comprises a conduit 106 having one end thereof incommunication with rotation motor conduit 101 and the other end thereofin communication with a choke assembly 108. A radial bore extendsthrough cylinder 12 and'opensinto a liner passageway 76. A radiallyinwardly extending portion of choke assembly 108 is suitably captivelyreceived within bore 110. Choke assembly 108 is constructed such that apredetermined measured amount of pressurized air passes therethrough.

With a start-up bolster assembly 104 as described hereinabove a flow ofpressurized air to the impact motor is initiated and, if freeze up ofpiston 14 occurs, pressurized air is supplied to the independent motor100 through conduit 101. A small amount of such pressurized air thenflows through assembly 104 into passageway 76, through passageway 78 andinto retracting chamber 80 thereby providing a sufficient pressuredifferential between chambers 80 and 81 to initiate the cyclic movementof piston 14. It is to be noted that the quantity of air flowing throughchoke assembly 108 is not sufficient to register any measurable decreasein the efficiency of the operation of rock drill 10. Also, in the eventit is desired to use the rotation motor 100 without activating thepiston 14, the quantity of air flowing through choke assembly 108 is notsufficient to initiate movement of the piston 14 if no other source ofpressurized air is flowing to the impact motor. Likewise, if it isdesired to operate the impact motor without operating the rotation motor100, the amount of air flowing through the choke assembly 108 will haveno effect on the standstill condition of motor 100.

Inasmuch as the invention herein resides in the method and apparatus forinitiating reciprocable movement of the piston 14, various modificationscan be made to the preferred embodiment described hereinabove withoutdeparting from the scope of the invention, for example: bolster assembly104 can communicate with groove 92 rather than groove 76 and hence theimpact chamber 82 will receive additional pressure rather than theretracting chamber 80 as described hereinabove; the bolster assembly 104can communicate directly with either the impact chamber 82 or theretracting chamber 80; a separate line from the fluid pressure sourcecan be provided for the bolster assembly 104 rather than tapping offconduit 101; a pilot operable check valve can be provided for selectiveoperation of bolster assembly 104; bolster assembly 104 can be used withrock drills of a type other than the rock drill described hereinabove;and the like.

The scope of the invention is defined by the claims set forthhereinafter.

What is claimed is:

1. A rock drill of a type having an elongated body with a chamberextending longitudinally therein, a hammer piston comprising a headportion and a stem portion reciprocable within said chamber throughimpacting, neutral and retracting positions for percussively actuating astriking bar upon movement of said piston within said chamber, with saidneutral position being axially intermediate said impacting andretracting positions and end portions of said chamber being pistonimpacting and retracting chamber portions, respectively, pistonpassageway means in said piston in communication with respective ones ofsaid chamber portions upon movement of said head portion of said pistoninto a respective chamber portion, the improvement comprising: firstpassageway means in said body being in communication with said pistonpassageway means during at least a major portion of said piston movementand adapted to be connected to a first fluid pressure source; and secondpassageway means in said body being in communication with only one ofsaid chamber portions during said piston movement and adapted to beconnected to a second fluid pressure source to provide initiation ofreciprocation of said piston when said piston is in said neutralposition.

2. A rock drill as specified in claim 1 wherein said second passagewaymeans provides pressure fluid to said selected one of said pistonchamber portions at a pressure less than the pressure of the pressurefluid supplied to said chamber by said first passageway means.

3. A rock drill as specified in claim 1 wherein said second fluidpassageway means comprises a conduit having one end thereof incommunication with said second fluid pressure source, and a valveassembly in said conduit adjacent the other end thereof.

4. A method of initiating cyclic movement of the hammer piston withinthe piston chamber of a rock drill wherein said piston reciprocatesthrough impacting, neutral and retracting positions and has passagewayscommunicating alternately with respective end portions of said chamberduring such cyclic movement comprising the steps of: supplying pressurefluid to one end portion of said piston chamber to provide initiation ofreciprocation of said piston when said piston is in said neutralposition; supplying pressure fluid to said end portions of said pistonchamber to maintain such cyclic movement; and said first mentionedsupplying being from a source of such pressure fluid independent of thesource of said second mentioned supplying.

5. A method as specified in claim 4 wherein said first and secondmentioned supplying take place substantially simultaneously.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 785248 Dated January 15 1974 Inventor(s) Edward A. Bailey It is certifiedthat error appears in the aboveeidentified patent andthat said LettersPatent are hereby corrected as shown below:

Claim rock drill as specified in claim 1 wherein said first and secondfluid pressure sources are supplied from a common supply means and eachof said sources are independently controlled.

Claim 7, A method as specified in claim 4- wherein said sources .ofpressure fluid are supplied from'a common supply means and each of saidsources are inde endently controlled.

On the cover sheet below "Abstract", "5 Claims" should read 7 ClaimsSigned and sealed this 23rd day of April 1971+.

(SEAL) Attest:

EDWARD I'I.FLETCIIEII,JR. G. MARSHALL DAi-IN Attesting OfficerCommissioner of Patents

1. A rock drill of a type having an elongated body with a chamberextending longitudinally therein, a hammer piston comprising a headportion and a stem portion reciprocable within said chamber throughimpacting, neutral and retracting positions for percussively actuating astriking bar upon movement of said piston within said chamber, with saidneutral position being axially intermediate said impacting andretracting positions and end portions of said chamber being pistonimpacting and retracting chamber portions, respectively, pistonpassageway means in said piston in communication with respective ones ofsaid chamber portions upon movement of said head portion of said pistoninto a respective chamber portion, the improvement comprising: firstpassageway means in said body being in communication with said pistonpassageway means during at least a major portion of said piston movementand adapted to be connected to a first fluid pressure source; and secondpassageway means in said body being in communication with only one ofsaid chamber portions during said piston movement and adapted to beconnected to a second fluid pressure source to provide initiation ofreciprocation of said piston when said piston is in said neutralposition.
 2. A rock drill as specified in claim 1 wherein said secondpassageway means provides pressure fluid to said selected one of saidpiston chamber portions at a pressure less than the pressure of thepressure fluid supplied to said chamber by said first passageway means.3. A rock drill as specified in claim 1 wherein said second fluidpassageway means comprises a conduit having one end thereof incommunication with said second fluid pressure source, and a valveassembly in said conduit adjacent the other end thereof.
 4. A method ofinitiating cyclic movement of the hammer piston within the pistonchamber of a rock drill wherein said piston reciprocates throughimpacting, neutral and retracting positions and has passagewayscommunicating alternately with respective end portions of said chamberduring such cyclic movement comprising the steps of: supplying pressurefluid to one end portion of said piston chamber to provide initiation ofreciprocation of said piston when said piston is in said neutralposition; supplying pressure fluid to said end portions of said pistonchamber to maintain such cyclic movement; and said first mentionedsupplying being from a source of such pressure fluid independent of thesource of said second mentioned supplying.
 5. A method as specified inclaim 4 wherein said first and second mentioned supplying take placesubstantially simultaneously.